The present invention relates to a device for perforating cigarette wrapping material by means of at least one laser beam.
In the cigarette industry, ventilated cigarettes are produced, normally consisting of a filter-tip cigarette, the cover band of the filter of which presents ventilation holes formed by means of a laser beam perforating device, for enabling the smoker to inhale, together with the smoke produced by combustion of the tobacco, a certain amount of air for reducing both the temperature and the amount of harmful substances contained in the smoke.
The formation, by means of laser beams, of ventilation holes for enabling the circulation of cooling air inside the cigarette is also useful in the case of plain cigarettes, i.e. without filters, in which case, the holes must be formed through a portion of the paper wrapping close to the mouth-held portion of the cigarette. Using a laser beam perforating device, however, plain cigarettes, unlike filter-tip types, do not permit formation of the ventilation holes on the finished cigarette, in which case, perforation of the paper wrapping would result in carbonization of the underlying tobacco.
The same also applies to filter-tip cigarettes featuring additional ventilation holes upstream from the filter, i.e. formed through a portion of the paper wrapping.
In the cigarette industry, the above problem is overcome, as described for example in U.S. Pat. No. 4,336,812, by forming the ventilation holes, using the laser method, in the paper wrapping prior to forming the cigarettes.
Such a method, however, involves several drawbacks as regards distribution of the holes in the paper wrapping, which, prior to forming the cigarettes, is normally in the form a continuous paper strip for producing a continuous cigarette rod. The formation of ventilation holes too close to the lateral edges of the paper strip, in fact, may result at later stages in transverse tearing of the strip.